In this blog post, we learn how to write a C Program to find the sum of natural numbers upto n.  We will take the help of iterative statements like for, while or do-while loop to find the SUM of the natural numbers.

What are Natural numbers?

Natural numbers are the positive integers or non-negative integers which starts from 1 and ends at infinity, such as:

1,2,3,4,5,6,7,8,9,10,……,∞

C Program to find the sum of natural numbers upto n using For Loop

In the below program, we will ask the user to enter the value of ‘n’. After entering the value of ‘n’ we will calculate the sum of natural numbers up to n terms with the help of for loop.

#include<stdio.h>

int main()
{
    int num, i;
    unsigned long int sum = 0;
    printf("Please Enter any Integer number = ");
    scanf("%d", &num);
    if(num >0)
    {
        for(i = 1; i <= num; i++)
        {
            sum += i;
        }

        printf("Sum = %ld\n",sum);
    }
    else
    {
        printf("Enter Valid number\n");
    }

    return 0;
}

Output:

Please Enter any Integer number = 5
Sum = 15

C Program to find the sum of natural numbers upto n using while Loop

In the below program, we will ask the user to enter the value of ‘n’. After entering the value of ‘n’ we will calculate the sum of natural numbers up to n terms with the help of a while loop.

#include<stdio.h>
int main()
{
    int num, i = 0;
    unsigned long int sum = 0;

    printf("Please Enter any Integer number = ");
    scanf("%d",&num);
    if(num >0)
    {
        while(i <= num)
        {
            sum += i;
            i++;
        }

        printf("Sum = %ld\n",sum);
    }
    else
    {
        printf("Enter Valid number\n");
    }
    return 0;
}

Output:

Please Enter any Integer number = 5
Sum = 15

C Program to find the sum of natural numbers within a range

The mentioned C Program to find the sum of natural numbers in a given range. The minimum and maximum value of the range ask by users.

#include<stdio.h>

int main()
{
    int rangeMinValue,rangeMaxValue, i;
    unsigned long int sum = 0;

    printf("Please Enter the rangeMinValue of natural number = ");
    scanf("%d",&rangeMinValue);

    printf("Please Enter the rangeMaxValue of natural number = ");
    scanf("%d",&rangeMaxValue);

    if((rangeMinValue > 0) && (rangeMaxValue > 0) && (rangeMaxValue > rangeMinValue ))
    {
        printf("List of Natural Numbers from %d to %d are \n",rangeMinValue,rangeMaxValue);
        for(i = rangeMinValue; i <= rangeMaxValue; i++)
        {
            sum += i;
        }

        printf("Sum = %ld\n",sum);
    }
    else
    {
        printf("Enter Valid numbers\n");
    }
    return 0;
}

Output:

Please Enter the rangeMinValue of natural number = 1
Please Enter the rangeMaxValue of natural number = 10
List of Natural Numbers from 1 to 10 are
Sum = 55